This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       To ensure applications portability, especially across natural languages, only  these  functions  and  the
       functions  in  the  reference  pages  listed  in  the  SEE  ALSO  section  should  be  used for character
       classification.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical  and  Electronics
       Engineers, Inc and The Open Group.  In the event of any discrepancy between this version and the original
       IEEE  and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document.
       The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                       ISALNUM(3POSIX)

       For isalnum(): The functionality described on this reference page is aligned with the ISO C standard. Any
       conflict  between the requirements described here and the ISO C standard is unintentional. This volume of
       POSIX.1‐2017 defers to the ISO C standard.

       The isalnum() and isalnum_l() functions shall test whether c is a character of class alpha  or  digit  in
       the current locale, or in the locale represented by locale, respectively; see the Base Definitions volume
       of POSIX.1‐2017, Chapter7, Locale.

       The c argument is an int, the value of which the application shall ensure is representable as an unsignedchar  or  equal  to  the  value  of  the  macro EOF. If the argument has any other value, the behavior is
       undefined.

       The behavior  is  undefined  if  the  locale  argument  to  isalnum_l()  is  the  special  locale  object
       LC_GLOBAL_LOCALE or is not a valid locale object handle.

       No errors are defined.

       Thefollowingsectionsareinformative.

       None.

       None.

       isalnum, isalnum_l — test for an alphanumeric character

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

       None.

       The  isalnum()  and  isalnum_l()  functions  shall  return  non-zero  if  c is an alphanumeric character;
       otherwise, they shall return 0.

isalpha(), isblank(),  iscntrl(),  isdigit(),  isgraph(),  islower(),  isprint(),  ispunct(),  isspace(),
       isupper(), isxdigit(), setlocale(), uselocale()

       The Base Definitions volume of POSIX.1‐2017, Chapter7, Locale, <ctype.h>, <stdio.h>

       #include <ctype.h>

       int isalnum(int c);
       int isalnum_l(int c, locale_t locale);